Interesting concept.
You are going to measure the PSU fan Speed/fan voltage with the Chroma loads. Later you will use the same voltage provided by a programmable PSU to spin the fan without the PSU switched on, am I right?

Thought about that, too, but I decided to go for real PC-systems. During noise testing I will stop all fans, so it should work.

I'm really interested if your anechoic chamber really works. The be quiet! kits should be decent quality and they are easy to get.